Vehicle power supply device

ABSTRACT

A vehicle power supply device that includes a control unit that performs at least a quick charging control which causes the first voltage converter to perform the charging operation and causes the second voltage converter to perform the charging operation, and a charging/discharging control which causes the first voltage converter to perform the charging operation and causes the second voltage converter to perform the discharging operation.

This application is the U.S. National Phase of PCT/JP2017/032890 filedSep. 12, 2017, which claims priority from JP 2016-193343 filed Sep. 30,2016, the entire disclosure of which is incorporated herein byreference.

BACKGROUND

The present disclosure relates to a vehicle power supply device.

In the field of power supply devices for vehicles, a backup system isknown that maintains a power supply to a load by performing the powersupply from an auxiliary power supply when a failure and the like occursin the main power supply. For example, the power supply system disclosedin JP 2013-176197 is configured such that the main power supply and abackup load are electrically connected through the power supply device.The backup load requires continual operation even when an abnormalitysuch as a reduction in the voltage of the main power supply or a failureoccurs. This system is configured so that power is continuously suppliedto the backup load from the power supply device even when the main powersupply has an abnormality.

SUMMARY

However, this type of power supply device requires that the auxiliarypower supply be charged at suitable periods. For example, when theoutput voltage of the auxiliary power supply is low immediately afterthe ignition switch has been switched on, the auxiliary power supplyrequires that the output voltage of the auxiliary power supply becharged up to a suitable level in which the backup operation is possibleafter the ignition switch has been switched on. However, in the existingtechnology in which a discharging operation is stopped during thecharging of the auxiliary power supply, there is a problem that when afailure or other abnormality occurs in the main power supply duringcharging, the power supply is cut off during the period from thedetection of the abnormality until the power supply from the auxiliarypower supply (backup operation) has started. Furthermore, this problemis more likely to occur as the charging period of the auxiliary powersupply grows longer.

An exemplary aspect of the disclosure provides a vehicle power supplydevice that is able to perform a quick charging operation in which thecharging time can be shortened when a second power supply unit ischarged with power from a first power supply unit, and acharging/discharging operation in which, even when the power supply ofthe first power supply unit is interrupted during charging, adischarging state can be maintained before and after the interruption.

A vehicle power supply device according to the present disclosure has: afirst conductive path electrically connected to a conductive path on aninput side that serves as a power pathway from a first power supply; asecond conductive path that is electrically connected to the conductivepath on the input side and branches off as a path different from thefirst conductive path, and is electrically connected to a conductivepath on an output side; a third conductive path that is electricallyconnected to the second conductive path and the conductive path on theoutput side; a first voltage converter that performs at least a chargingoperation for stepping up or stepping down the voltage applied to thefirst conductive path and applying an output voltage to a conductivepath on a second power supply side connected to the second power supply;a second voltage converter that performs at least a charging operationfor stepping up or stepping down a voltage applied to the thirdconductive path and applying an output voltage to the conductive path onthe second power supply side, and a discharging operation for steppingup or stepping down a voltage applied to the conductive path on thesecond power supply side and applying an output voltage to the thirdconductive path; and a control unit that performs at least a quickcharging control which causes the first voltage converter to perform thecharging operation and causes the second voltage converter to performthe charging operation, and a charging/discharging control which causesthe first voltage converter to perform the charging operation and causesthe second voltage converter to perform the discharging operation.

The vehicle power supply device is able to cause both the first voltageconverter and the second voltage converter to perform the chargingoperation when the control unit performs the quick charging control.Because the charging time of the second power supply can be shorteneddue to the quick charging control, the charging voltage of the secondpower supply can be easily raised to a suitable level earlier, and asituation in which the timing of the power supply being cut off arrivesduring the quick charging control is less likely to occur.

In addition, the first voltage converter is caused to perform thecharging operation and the second voltage converter is caused to performthe discharging operation when the control unit performs thecharging/discharging control. That is, during the charging/dischargingcontrol, even when, hypothetically, the power supply from the firstpower supply is interrupted during the charging by means of thecharging/discharging control, the charging state of the second powersupply is continuously maintained before and after the interruptionbecause the discharging operation of the second power supply can becontinued by the second voltage converter while the charging operationof the second power supply is being performed by the first voltageconverter.

Furthermore, because two useful controls can be used separately withregard to the “problem of the power supply of the first power supplyunit being cut off during charging” in this way, the above problem canbe addressed and freedom for charging the second power supply unit canbe enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram schematically showing a vehicle power supplysystem provided with a vehicle power supply device according to a firstembodiment.

FIG. 2 is a flow chart showing a charging control flow performed afterthe ignition is turned on in the vehicle power supply device accordingto the first embodiment.

FIG. 3 is a diagram for explaining an operating state during a quickcharging control of the vehicle power supply device according to thefirst embodiment.

FIG. 4 is a diagram for explaining an operating state during acharging/discharging control of the vehicle power supply deviceaccording to the first embodiment.

FIG. 5 is a diagram for explaining an operating state during a one-sidedischarging control of the vehicle power supply device according to thefirst embodiment.

FIG. 6 is a diagram for explaining an operating state during a quickdischarging control of the vehicle power supply device according to thefirst embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

A desirable mode of the disclosure is described below.

A control unit may function so as to perform a quick charging controlwhen a starting switch for switching a vehicle in which the power sourcedevice is mounted to a state in which travel is possible, is turned on,and a charging/discharging control when a predetermined condition isestablished after the starting switch has been turned on.

This vehicle power supply device is capable of promptly increasing anoutput voltage because charging can be performed quickly after thestarting switch has been turned on even when the output voltage of asecond power supply unit (second power supply) is at a relatively lowlevel at the point in time that the starting switch is turned on. Thatis, the second power supply unit can recover from a low level state atan early stage after the starting switch has been turned on. When apredetermined condition has been established after starting the quickcharging control, the quick charging control can be completed at anearly stage and switched to the charging/discharging control that isresistant to a power interruption of the first power supply unit (firstpower supply) (a control in which, even if the power is interrupted, thedischarging is maintained at that point in time).

The control unit may function so as to perform the charging/dischargingcontrol when at least a shift operation of the vehicle in which thepower source device is mounted is performed after the starting switchhas been turned on.

The vehicle power supply device is able to promptly increase the outputvoltage of the second power supply unit before the vehicle travels andthe second power supply unit can be recovered at an earlier stage from alow level state because the quick charging control can be performedbefore the shift operation is performed. The control can at least beswitched to the charging/discharging control after the shift operationhas been performed. That is, after the possibility of the vehicleentering a traveling state has been established, the complete cutoff ofpower during traveling can be prevented by switching to a control thatis resistant to a power interruption of the first power supply unit (acontrol in which, even when a power interruption occurs, discharging ismaintained at that point in time).

The control unit may function so as to perform the charging/dischargingcontrol when at least a fixed time period has elapsed after the startingswitch has been turned on.

During an initial stage after the starting switch has been turned on andbefore the fixed time period has elapsed, the vehicle power supplydevice is able to promptly increase the output voltage of the secondpower supply unit and cause the second power supply unit to recover froma low level state at an earlier stage because the quick charging controlcan be performed. After at least the fixed time period has elapsed, thecontrol can be switched to the charging/discharging control that isresistant to a power interruption of the first power supply unit (acontrol in which, even if the power is interrupted, the discharging ismaintained at that point in time).

The vehicle power supply device may have a switching unit (switch)provided with: a switch part that is disposed in the third conductivepath, has one end electrically connected to the second voltageconversion unit (second voltage converter), has the other endelectrically connected to the conductive path on the output side, andswitches between on and off; and a diode that is provided in parallel tothe switch part, has an anode electrically connected to the secondvoltage conversion unit, and a cathode electrically connected to theconductive path on the output side. The control unit may function so asto perform the quick charging control while the switch part is turnedon, and perform the charging/discharging control while the switch partis turned off.

While performing the quick charging control, the vehicle power supplydevice is able to allow a current to flow to the second voltageconversion unit from the conductive path on the input side through thesecond conductive path and the third conductive path by turning on theswitch part of the switching unit. Moreover, while performing thecharging/discharging control, the vehicle power supply device allows acurrent output from the second voltage conversion unit to flow towardthe conductive path on the output side due to the presence of the diodeprovided in parallel with the switch part, while interrupting the flowof the current from the conductive path on the input side, through thesecond conductive path and the third conductive path, to the secondvoltage conversion unit, by turning the switch part off.

The vehicle power supply device may be provided with an abnormalitydetection unit (abnormality detector) that detects at least anabnormality of the voltage or current of the conductive path on theinput side. The control unit may function so as to perform a one-sidedischarging control in which operation of the first voltage conversionunit (first voltage converter) is stopped and the second voltageconversion unit is caused to perform a discharging operation when anabnormality is detected by the abnormality detection unit when the quickcharging control or the charging/discharging control is being performed.

The control unit of the vehicle power supply device performs theone-side discharging control when the abnormality detection unit detectsan abnormality while the quick charging control or thecharging/discharging control is being performed. Due to the one-sidedischarging control, the operation of the first voltage conversion unitis stopped for protection and the second voltage conversion unit iscaused to perform the discharging operation to maintain a power supplystate. In particular, when the control is switched to the one-sidedischarging control when an abnormality occurs on the conductive path onthe input side while the charging/discharging control is beingperformed, a situation is less likely to occur in which the power supplyimmediately after the occurrence of the abnormality is completelycutoff, because the discharging operation of the second voltageconversion unit can be continued before and after the abnormality.

The vehicle power supply device may have a second switching unit (secondswitch) for switching between on in which the flow of current betweenthe conductive path on the input side and the third conductive path isallowed and off in which said flow is interrupted. The control unit mayfunction so as to turn on the second switching unit when the controlunit executes the quick charging control and the charging/dischargingcontrol, and may turn off the second switching unit when the controlunit executes the one-side discharging control.

When performing the quick charging control, the vehicle power supplydevice turns on the second switching unit (state for allowing the flowof a current between the conductive path on the input side and the thirdconductive path) and enables the current to be supplied from theconductive path on the input side, through the second conductive pathand the third conductive path, to the second voltage conversion unit.However, when the one-side discharging control is being performed inresponse to the occurrence of an abnormality, a charging current fromthe second voltage conversion unit can be prevented from mistakenlyflowing into the conductive path on the input side where the abnormalityhas occurred because the second switching unit can be turned off.

The first voltage conversion unit may perform a charging operation forstepping up or stepping down the voltage applied to the first conductivepath and outputting the output voltage to the conductive path on thesecond power supply unit side, and a discharging operation for steppingup or stepping down the voltage applied to the conductive path on thesecond power supply unit side and outputting the voltage to the firstconductive path. The control unit may function so as to at least performa quick discharging control for causing the second voltage conversionunit to perform the discharging operation while causing the firstvoltage conversion unit to perform the discharging operation.

The vehicle power supply device is able to cause either of the firstvoltage conversion unit and the second voltage conversion unit toperform the discharging operation as needed which is advantageous whenit is desirable to increase the discharging capacity of the second powersupply unit.

The vehicle power supply device may have a voltage detection unit fordetecting the output voltage of the second power supply unit. Thecontrol unit may function so as to perform the quick discharging controlwhen at least the output voltage of the second power supply unitdetected by the voltage detection unit is equal to or less than a fixedvalue.

The second power supply unit may be used until a low voltage range ifthe quick discharging control is performed when the output voltage ofthe second power supply unit is reduced. Consequently, the voltage rangein which use of the second power supply unit is possible can be widened.

The vehicle power supply device may have a plurality of the firstconductive paths that branch off from the conductive path on the inputside. Further, a multiphase configuration may be formed in which aplurality of the first voltage conversion units are provided in parallelbetween the respective first conductive paths and the conductive path onthe second power supply unit side.

The vehicle power supply device is able to improve the charging capacitybecause the multiphase configuration is formed in which a plurality ofthe first voltage conversion units are provided in parallel.

The vehicle power supply device may have a plurality of the thirdconductive paths. Further, a multiphase configuration may be formed inwhich a plurality of the second voltage conversion units are provided inparallel between the conductive path on the second power supply unitside and the respective third conductive paths.

The vehicle power supply device is able to improve the dischargingcapacity because the multiphase configuration is formed in which aplurality of the second voltage conversion units are provided inparallel. In addition, even if an open fault or the like occurs in anyof the second voltage conversion units during the charging/dischargingcontrol, the power supply can be easily maintained by means of adischarging operation using another second voltage conversion unit.

First Embodiment

A first embodiment that embodies the present disclosure is explainedbelow.

A vehicle power supply system 100 shown in FIG. 1 is provided with afirst power supply unit 3, a second power supply unit 5, and a vehiclepower supply device 1 (may be referred to hereinbelow as power supplydevice 1), and is configured as a system that can supply power to aload. The second power supply unit 5 may be configured as a portion ofthe power supply device 1 or may be provided as a member separate fromthe power supply device 1. In the following explanation, an example inwhich the second power supply unit 5 is configured as a portion of thepower supply device 1 will be explained as a representative example.

The first power supply unit 3 is, for example, configured by awell-known power storage means such as a lead storage battery. The firstpower supply unit 3 generates a predetermined voltage and applies thepredetermined voltage to a conductive path 14 on the input side. Aterminal on the high potential side of the first power supply unit 3 iselectrically connected to the conductive path 14 on the input side thatforms a power pathway from the first power supply unit 3, and a terminalon the low potential side of the first power supply unit 3 iselectrically connected to a ground.

The second power supply unit 5 is configured, for example, by awell-known power storage means such as an electric double layercapacitor. The second power supply unit 5 is, for example, configured asa capacitor group in which a plurality of capacitors are connected inseries, and a terminal that serves as the lowest potential in theentirety is electrically connected to a ground via a current detectionresistance (a resistor 82A). In addition, a terminal that serves as thehighest potential in the second power supply unit 5 is electricallyconnected to a conductive path 24 on the second power supply unit side.

The power supply device 1 is mainly provided with: a first voltageconversion unit 40; a second voltage conversion unit 50; a control unit60; a first conductive path 21; a second conductive path 22; a thirdconductive path 23; the conductive path 24 on the second power supplyunit side; the second power supply unit 5; semiconductor switches 71,72, 73; and current detection circuits 81, 82, 83, etc. The aboveelements are provided as an integrated unit on a substrate which is notillustrated.

The power supply device 1 is configured as a circuit that generates anoutput voltage to be applied to a conductive path 16 on the output side,based on the voltage applied to the conductive path 14 on the input sideby the first power supply unit 3, and as a circuit that generates anoutput voltage to be applied to the conductive path 16 on the outputside based on the voltage applied to the conductive path 24 on thesecond power supply unit side by the second power supply unit 5 when thevoltage applied to the conductive path 14 on the input side has fallenbelow a fixed level. Within the wiring that forms the conductive path 14on the input side in FIG. 1, the wiring that is provided on thesubstrate that configures the power supply device 1 is referred to asthe conductive path 14B, and the wiring that is provided outside of thepower supply device 1 is referred to as the conductive path 14A. Inaddition, within the wiring that forms the conductive path 16 on theoutput side, the wiring that is provided on the substrate thatconfigures the power supply device 1 is referred to as the conductivepath 16B, and the wiring that is provided outside of the power supplydevice 1 is referred to as the conductive path 16A.

The power supply device 1 is provided with the first conductive path 21and the second conductive path 22 that branch off from the conductivepath 14 on the input side, and the third conductive path 23 and theconductive path 16B that branch off from the second conductive path 22.

The first conductive path 21 is a conductive path that connects theconductive path 14 on the input side and the first voltage conversionunit 40. The first conductive path 21 functions as a pathway forapplying the voltage of the conductive path 14 on the input side to adrain of a switching element 41 so that the voltage of the conductivepath 14 on the input side becomes the input voltage of the first voltageconversion unit 40 during a step-down operation of the first voltageconversion unit 40. In addition, the first conductive path 21 functionsas a pathway for transmitting the output voltage so that the outputvoltage of the first voltage conversion unit 40 is applied to the secondconductive path 22 during a step-up operation of the first voltageconversion unit 40.

The second conductive path 22 branches off from the conductive path 14on the input side as a pathway different from the first conductive path21, and is electrically connected to the conductive path 16B (a portionof the conductive path 16 on the output side) and the third conductivepath 23. The second conductive path 22 functions as a conductive pathfor connecting the conductive path 14 on the input side with theconductive path 16 on the output side and the third conductive path 23.

The third conductive path 23 is a conductive path for connecting thesecond conductive path 22 and the conductive path 16 on the output sidewith the second voltage conversion unit 50, and functions as a pathwayfor applying, to a drain of a switching element 51, an input voltagebased on the voltage of the second conductive path 22 during a step-downoperation of the second voltage conversion unit 50. In addition, thethird conductive path 23 functions as a pathway for transmitting theoutput voltage so that the voltage based on the output voltage of thesecond voltage conversion unit 50 is applied to the conductive path 16on the output side during a step-up operation of the second voltageconversion unit 50.

The conductive path 24 side (fourth conductive path) of the second powersupply unit is a conductive path for connecting an inductor 43 of thefirst voltage conversion unit 40, and an inductor 53 of the secondvoltage conversion unit 50, and a terminal on the high potential side ofthe second power supply unit 5, and is a conductive path to which theoutput voltage (charging voltage) of the second power supply unit 5 isapplied.

The semiconductor switches 71 and 72 are configured, for example, asN-channel MOSFETs. The semiconductor switches 71 and 72 correspond to anexample of a second switching unit, and function so as to switch betweenon, in which the current between the conductive path 14 on the inputside and the third conductive path 23 is allowed to flow, and off, inwhich said current is interrupted. Specifically, if the semiconductorswitches 71 and 72 are both on, energization between the conductive path14 on the input side and the third conductive path 23 is possible, andif the semiconductor switches 71 and 72 are both off, energizationbetween the conductive path 14 on the input side and the thirdconductive path 23 is possible. The drain of the semiconductor switch 71is electrically connected to the first power supply unit 3 via theconductive path 14B that forms a portion of the conductive path 14 onthe input side, and the source of the semiconductor switch 71 iselectrically connected to the first conductive path 21 and the secondconductive path 22. When the semiconductor switch 71 is off, the flow ofthe current from the first conductive path 21 and the second conductivepath 22 toward the first power supply unit 3 is interrupted. When thesemiconductor switch 71 is on, energization in both directions along theconductive path 14B is allowed. The drain of the semiconductor switch 72is electrically connected to the conductive path 16 on the output sideand the first power supply unit 3, and the source of the semiconductorswitch 72 is electrically connected to the first conductive path 21 andthe second conductive path 22. When the semiconductor switch 72 is off,the flow of the current from the conductive path 14 on the input sideand the first conductive path 21 to the conductive path 16 on the inputside and the third conductive path 23 is interrupted. When thesemiconductor switch 72 is on, energization in both directions along thesecond conductive path 22 is allowed.

The semiconductor switch 73 is configured, for example, as an N-channelMOSFET. The semiconductor switch 73 corresponds to an example of aswitching unit, and switches between on, in which energization in bothdirections of the third conductive path 23 is allowed, and off, in whichenergization in the direction toward the second voltage conversion unit50 along the third conductive path 23 is interrupted. A portion of thesemiconductor switch 73 excluding a body diode 73A (also referred tobelow as a diode 73A) is a switch part 73B. The switch part 73B isdisposed in the third conductive path 23 and one end of the switch part73B is electrically connected to the second voltage conversion unit 50,the other end thereof is electrically connected to the conductive path16 on the output side, and the switch part 73B is switched between onand off. When the switch part 73B is on, energization in both directionsalong the third conductive path 23 is allowed. The diode 73A is providedin parallel to the switch part 73B, and the anode of the diode 73A iselectrically connected to the second voltage conversion unit 50, and thecathode thereof is electrically connected to the conductive path 16 onthe output side.

The first voltage conversion unit 40 is a synchronous rectification-typesingle phase DCDC converter and is provided between the first conductivepath 21 and the conductive path 24 on the second power supply unit side.The first voltage conversion unit 40 functions as a step-up/step-downbidirectional DCDC converter having the function of using the voltageapplied to the first conductive path 21 as an input voltage and steppingdown and outputting said input voltage to the conductive path 24 on thesecond power supply unit side and connected to the second power supplyunit 5 (function for performing a charging operation), and the functionof using the voltage applied to the conductive path 24 on the secondpower supply unit as an input voltage, and stepping up and outputtingsaid input voltage to the first conductive path 21 (function forperforming a discharging operation).

The first voltage conversion unit 40 is provided with the switchingelement 41 on the high side and a switching element 42 on the low side,both of which are configured as N-channel MOSFETs, the inductor 43, anda capacitor 44. The switching element 41 and the switching element 42are connected in series between the first conductive path 21 and aground, and the drain of the switching element 41 is connected to thefirst conductive path 21 and receives the application of the voltage ofthe first conductive path 21. The source of the switching element 41 isconnected to the drain of the switching element 42 on the low side andto one end of the inductor 43. The source of the switching element 42 isconnected to the ground via a resistor 83A. Drive signals (on-signals)and non-drive signals (off-signals) are inputted to the gate of theswitching element 41 by means of PWM signals from a drive circuitprovided in the control unit 60, and the switching element 41 isswitched between on and off in response to the signals from the drivecircuit. Similarly, drive signals (on-signals) and non-drive signals(off-signals) are inputted to the gate of the switching element 42 bymeans of the PWM signals from the drive circuit, and the switchingelement 42 is switched between on and off in response to the signalsfrom the drive circuit.

The drive circuit provided in the control unit 60 applies, to the gatesof the switching elements 41 and 42, on-signals for alternately turningon the switching elements 41 and 42 according to the respective controlperiods. On-signals whose phases are substantially inverted from thoseof the on-signals applied to the gate of the switching element 42 andfor which a so-called dead time is assured, are applied to the gate ofthe switching element 41.

The second voltage conversion unit 50 is a synchronousrectification-type single phase DCDC converter and is provided betweenthe third conductive path 23 and the conductive path 24 on the secondpower supply unit side. The second voltage conversion unit 50 functionsas a step-up/step-down bidirectional DCDC converter having the functionof using the voltage applied to the third conductive path 23 as an inputvoltage and stepping down and outputting said input voltage to theconductive path 24 on the second power supply unit side (function forperforming a charging operation), and the function of using the voltageapplied to the conductive path 24 on the second power supply unit as aninput voltage, and stepping up and outputting said input voltage to thethird conductive path 23 (function for performing a dischargingoperation).

The second voltage conversion unit 50 is provided with a switchingelement 51 on the high side and a switching element 52 on the low side,both of which are configured as N-channel MOSFETs, the inductor 53, anda capacitor 54. The switching element 51 and the switching element 52are connected in series between the third conductive path 23 and aground. The drain of the switching element 51 is connected to the thirdconductive path 23 and receives the application of the voltage of thethird conductive path 23. The source of the switching element 51 isconnected to the drain of the switching element 52 on the low side andto one end of the inductor 53. The source of the switching element 52 isconnected to the ground via the resistor 83A. Drive signals (on-signals)and non-drive signals (off-signals) are inputted to the gate of theswitching element 51 by means of the PWM signals from the drive circuitprovided in the control unit 60, and the switching element 51 isswitched between on and off in response to the signals from the drivecircuit. Similarly, drive signals (on-signals) and non-drive signals(off-signals) are inputted to the gate of the switching element 52 bymeans of the PWM signals from the drive circuit, and the switchingelement 52 is switched between on and off in response to the signalsfrom the drive circuit.

The drive circuit provided in the control unit 60 applies, to the gatesof the switching elements 51 and 52, on-signals for alternately turningon the switching elements 51 and 52 according to the respective controlperiods. On-signals whose phases are substantially inverted from thoseof the on-signals applied to the gate of the switching element 52 andfor which a so-called dead time is assured, are applied to the gate ofthe switching element 51.

The control unit 60 is provided with a control circuit that isconfigured, for example, as a microcomputer, and the drive circuit foroutputting the PWM signals to the switching elements 41, 42, 51, and 52on the basis of the PWM signals issued by the control circuit. Thecontrol circuit provided in the control unit 60 is provided with: a CPUthat can perform various operations; a ROM for storing information suchas programs; a RAM for storing temporarily generated information; and anA/D converter for converting an analog voltage to a digital value. TheCPU is connected by a bus to the ROM, the RAM, and the A/D converter.

The current detection circuit 81 has a resistor 81A and a differentialamplifier 81B. A voltage drop produced by the resistor 81A is amplifiedby the differential amplifier 81B and becomes a detection voltage thatcorresponds to an output current, and is converted to a digital value bythe A/D converter. The current detection circuit 82 has a resistor 82Aand a differential amplifier 82B. A voltage drop produced by theresistor 82A is amplified by the differential amplifier 82B and becomesa detection voltage that corresponds to an output current, and isconverted to a digital value by the A/D converter. The current detectioncircuit 83 has the resistor 83A and a differential amplifier 83B. Avoltage drop produced by the resistor 83A is amplified by thedifferential amplifier 83B and becomes a detection voltage thatcorresponds to an output current, and is converted to a digital value bythe A/D converter.

The detection voltages from the current detection circuits 81 to 83 areinputted to an A/D converter in the control unit 60, and the voltagesthereof are changed to digital values by the A/D converter, whereby thecontrol circuit in the control unit 60 is able to detect the currents atthe positions where the resistors 81A, 82A, and 83A are provided. Inaddition, the respective voltages of the conductive path 14 on the inputside, the conductive path 24 on the second power supply unit side, andthe third conductive path 23 are inputted to the A/D converter in thecontrol unit 60, and the respective voltages are changed to digitalvalues by the A/D converter whereby the control circuit in the controlunit 60 is able to detect the voltages of the respective positions.While the example of FIG. 1 illustrates an example configuration inwhich the respective voltages of the conductive path 14 on the inputside, the conductive path 24 on the second power supply unit side, andthe third conductive path 23 are input directly to the control unit 60,a voltage divider circuit may be provided for dividing the respectivevoltages of the conductive path 14 on the input side, the conductivepath 24 on the second power supply unit side, and the third conductivepath 23, and the divided voltages of the respective voltages may beinputted to the control unit 60.

The control unit 60 causes the first voltage conversion unit 40 tofunction as a synchronous rectification step-up/step-down converter, andwhen performing a step-down operation, the control unit 60 synchronizesthe switching of the on- and off-operations of the switching element 42on the low side with the operations of the switching element 41 on thehigh side, whereby a direct current voltage applied to the firstconductive path 21 is stepped down and outputted to the conductive path24 on the second power supply unit side. The output voltage of theconductive path 24 on the second power supply unit side is determined inaccordance with the duty ratio of the PWM signals applied to the gate ofthe switching element 41. When performing a step-down operation, thecontrol unit 60 performs a feedback operation using a well-knownfeedback operation method (for example, a PID operation method) andadjusts the duty of the PWM signals so that the output voltageapproaches a predetermined target voltage on the basis of a deviationbetween the output voltage applied to the conductive path 24 on thesecond power supply unit side and the target voltage.

When performing a step-up operation with the first voltage conversionunit 40, the control unit 60 performs a feedback operation using awell-known feedback operation method (for example, a PID operationmethod) and adjusts the duty of the PWM signals so that the outputvoltage approaches a predetermined target voltage on the basis of adeviation between the output voltage applied to the first conductivepath 21 and the target voltage.

In addition, the control unit 60 causes the second voltage conversionunit 50 to function as a synchronous rectification step-up/step-downconverter, and when performing a step-down operation, the control unit60 synchronizes the switching of the on- and off-operations of theswitching element 52 on the low side with the operations of theswitching element 51 on the high side, whereby a direct current voltageapplied to the third conductive path 23 is stepped down and outputted tothe conductive path 24 on the second power supply unit side. The outputvoltage of the conductive path 24 on the second power supply unit sideis determined in accordance with the duty ratio of the PWM signalsapplied to the gate of the switching element 51. When performing astep-up operation, the control unit 60 performs a feedback operationusing a well-known feedback operation method (for example, a PIDoperation method) and adjusts the duty of the PWM signals so that theoutput voltage approaches a predetermined target voltage on the basis ofa deviation between the output voltage applied to the conductive path 24on the second power supply unit side and the target voltage.

When performing a step-up operation with the second voltage conversionunit 50, the control unit 60 performs a feedback operation using awell-known feedback operation method (for example, a PID operationmethod) and adjusts the duty of the PWM signals so that the outputvoltage approaches a predetermined target voltage on the basis of adeviation between the output voltage applied to the third conductivepath 23 and the target voltage.

The methods for setting the proportional gain, the derivative gain, andthe integration gain are not limited when performing the feedbackoperation with the PID method, and any setting method may be used.

In the present configuration, the control unit 60 is able to perform atleast four controls: the quick charging control, thecharging/discharging control, the one-side discharging control, and thequick discharging control. The quick charging control is a control forcausing the first voltage conversion unit 40 to perform a chargingoperation and causing the second voltage conversion unit 50 to perform acharging operation. The charging/discharging control is a control forcausing the first voltage conversion unit 40 to perform a chargingoperation and causing the second voltage conversion unit 50 to perform adischarging operation. The one-side discharging control is a control forstopping the charging operation of the first voltage conversion unit 40and causing the second voltage conversion unit 50 to perform adischarging operation. The quick discharging control is a control forcausing the first voltage conversion unit 40 to perform a dischargingoperation and causing the second voltage conversion unit 50 to perform adischarging operation.

Next, a flow of the specific controls executed by the power supplydevice 1 will be explained.

The control described in FIG. 2 is, for example, a process that isexecuted when a starting switch is turned on for switching a vehicle inwhich the power supply device 1 is mounted to a state in which travel ispossible. Specifically, when an unillustrated ignition switch providedin a vehicle is switched from on to off, an ignition on-signal (may bereferred to below as IG on-signal) which indicates that the ignitionswitch has been turned on is input into the control unit 60 from adevice (an external ECU or the like) provided outside of the powersupply device 1. When the ignition switch is turned off, an ignitionoff-signal (may be referred to below as IG off-signal) which indicatesthat the ignition switch has been turned off is input into the controlunit 60. That is, the ignition switch corresponds to an example of thestarting switch, and the case of the ignition switch being turned oncorresponds to an example of “when the starting switch is turned on.”

The control unit 60 first executes the processing of step S1 and setsthe mode for operating the power supply device 1 to a quick chargingmode when the control in FIG. 2 is started in response to the ignitionswitch being turned on. The quick charging mode is a mode for thecontrol unit 60 to perform the quick charging control. During the quickcharging control, the control unit 60 keeps the semiconductor switches71 and 72 on and keeps the semiconductor switch 73 on. While theswitches are on, both the first voltage conversion unit 40 and thesecond voltage conversion unit 50 are caused to perform the chargingoperation for supplying a charging current to the second power supplyunit 5 as illustrated in FIG. 3. Specifically, the first voltageconversion unit 40 is caused to perform a step-down operation so as tostep-down the voltage of the first conductive path 21 and output thevoltage to the conductive path 24 of the second power supply unit side,and the second voltage conversion unit 50 is caused to perform astep-down operation so as to step-down the voltage of the thirdconductive path 23 and output the voltage to the conductive path 24 ofthe second power supply unit side. During the quick charging control inthis way, a charging current is supplied to the second power supply unit5 by the first voltage conversion unit 40 and the second voltageconversion unit 50 and a relatively large charging current is supplied,whereby the raising speed of the charging voltage is increased.

In this way, the control unit 60 performs the quick charging controlwhen the starting switch (specifically, the ignition switch) forswitching the vehicle in which the power supply device 1 is mounted to astate in which travel is possible, and the quick charging control iscontinued until a predetermined completion condition is established(until a quick charging completion trigger is reached).

The control unit 60 sets the quick charging mode in step S1, and afterthe quick charging control has started, determines whether thepredetermined completion condition has been established (whether thequick charging completion trigger has been reached) in step S2. In thepresent configuration, the “predetermined completion condition” isdetermined when a shift operation is performed in the vehicle in whichthe power supply device 1 is mounted, or when a fixed time period haselapsed since the ignition switch (starting switch) has been turned on.When the control unit 60 determines that the completion condition hasnot been established in step S2, namely, when a shift operation has notbeen performed in the vehicle in which the power supply device 1 ismounted, or when the fixed time period has not elapsed since theignition switch (starting switch) has been turned on (No in step S2),the control unit 60 continues the quick charging mode in step S1.

When the control unit 60 determines that the completion condition hasbeen established in the processing step S2, namely when a shiftoperation has been performed in the vehicle in which the power supplydevice 1 is mounted, or when the fixed time period has elapsed since theignition switch (starting switch) has been turned on (Yes in step S2),the control unit 60 performs the processing in step S3 and switches themode from the quick charging mode to normal charging mode(charging/discharging mode). That is, the control unit 60 performs thecharging/discharging control when a shift operation has been performedin the vehicle in which the power supply device 1 is mounted after theignition switch (starting switch) has been turned on, or when the fixedtime period has elapsed after the starting switch was turned on.

In the present configuration, a signal indicating a shift range is inputto the power supply device 1 from an external device (for example, ashift-by-wire ECU or the like) provided outside of the power supplydevice 1, and the feature of “when a signal indicating a new shift rangeis input to the power supply device 1 after the ignition switch has beenturned on” corresponds to an example of “when a shift operation hasoccurred.” For example, a P-range signal indicating that the shift rangehas entered a P-range immediately after the ignition switch has beenturned on, is input to the power supply device 1, and the control unit60 determines that a shift operation has occurred when a D-range signalwhich indicates that the shift range has entered a D-range before thefixed time period from when the ignition switch (starting switch) hasbeen turned on, has elapsed. The routine then advances to Yes in stepS2.

The normal charging mode (charging/discharging mode) set in step S3 is amode in which the control unit 60 performs the charging/dischargingcontrol. The control unit 60 keeps both of the semiconductor switches 71and 72 on, and switches the semiconductor switch 73 off during thenormal charging mode (charging/discharging mode). According to the aboveswitch conditions, the first voltage conversion unit 40 is caused toperform the charging operation (step-down operation) for supplying thecharging current to the second power supply unit 5, and the secondvoltage conversion unit 50 is caused to perform the dischargingoperation (step-up operation) in which the discharging current flows asillustrated in FIG. 4. Specifically, the first voltage conversion unit40 is caused to perform a step-down operation so as to step-down thevoltage of the first conductive path 21 and output the voltage to theconductive path 24 of the second power supply unit side, and the secondvoltage conversion unit 50 is caused to perform a step-up operation soas to step-up the voltage of the conductive path 24 of the second powersupply unit side and output the voltage to the third conductive path 23.

When the control unit 60 performs the quick charging control asillustrated in FIG. 3, the semiconductor switch 73 is kept off (that is,the switch part 73B is on). However, when the control unit 60 performsthe charging/discharging control as illustrated in FIG. 4, thesemiconductor switch 73 is kept on (that is, the switch part 73B isoff). Specifically, during the charging/discharging control, the flow ofthe current toward the second voltage conversion unit 50 from the secondconductive path 22 through the third conductive path 23 is interrupted,and the current output from the second voltage conversion unit 50 to thethird conductive path 23 flows through the body diode 73A to theconductive path 16 on the output side.

After the control unit 60 sets the mode to the normal charging mode(charging/discharging mode) in step S3, the control unit 60 determineswhether a backup trigger has been reached (specifically, whether anabnormality of the power supply from the conductive path 14 on the inputside has occurred) in step S4. According to the present configuration,the voltage of the conductive path 14 on the input side is input to thecontrol unit 60, and the control unit 60 monitors the voltage of theconductive path 14 on the input side. The control unit 60 determines instep S4 whether the voltage of the conductive path 14 on the input sideis equal to or less than a first threshold voltage. If the voltage ofthe conductive path 14 on the input side is equal to or less than thefirst threshold voltage (when it is determined that the backup triggerhas occurred, Yes in step S4), the processing in step S6 is performed.

When the control unit 60 determines in step S4 that the voltage of theconductive path 14 on the input side has exceeded the first thresholdvoltage (the control unit 60 determines that the backup trigger has notoccurred, No in step S4), the control unit 60 determines whether acharging completion condition has been established (for example, whetherthe charging voltage of the second power supply unit 5 has reached acharging threshold voltage) in step S5. When the control unit 60determines in step S5 that the charging completion condition has notbeen established (No in step S5), the control unit 60 performs theprocessing from step S3 onward.

When the control unit 60 determines in step S5 that the chargingcompletion condition has been established (Yes in step S5), the controlunit 60 completes the abovementioned charging/discharging control (FIG.4) and stops the operations of the first voltage conversion unit 40 andthe second voltage conversion unit 50. In this case, after thecharging/discharging control has been completed, for example, thesemiconductor switch 73 is kept off while the semiconductor switches 71and 72 are kept on.

When the control unit 60 determines in step S4 that the voltage of theconductive path 14 on the input side is equal to or less than the firstthreshold voltage and performs the processing in step S6, the controlunit 60 sets the mode to a first backup mode (one-side dischargingmode). The first backup mode (one-side discharging mode) is a mode forthe control unit 60 to perform the one-side discharging control. Thecontrol unit 60 keeps both of the semiconductor switches 71 and 72 offand keeps the semiconductor switch 73 on when performing the one-sidedischarging control. As a result, the flow of the current from the firstconductive path 21 and the second conductive path 22 toward theconductive path 14 on the input side is interrupted, and the flow of thecurrent from the conductive path 14 on the input side and the firstconductive path 21 toward the conductive path 16 on the output side isalso interrupted. According to the above switch conditions, theoperation of the first voltage conversion unit 40 is stopped and thesecond voltage conversion unit 50 is caused to perform the dischargingoperation (step-up operation) in which a discharging current flows asillustrated in FIG. 5. Specifically, the second voltage conversion unit50 is caused to perform the step-up operation so that the switchingelements 41 and 42 of the first voltage conversion unit 40 are kept offand the voltage of the conductive path 24 on the second power supplyunit side is stepped-up and output to the third conductive path 23.

In this way, even if a voltage drop of the conductive path 14 on theinput side occurs due to a ground fault or disconnection and the likewhile the second power supply unit 5 is being charged with theabovementioned charging/discharging control, the second power supplyunit 5 can be caused to operate as a backup power supply by performingthe one-side discharging control. Moreover, because the discharging bythe second voltage conversion unit 50 can be maintained withoutinterruption before and after the control unit 60 switches the controlfrom the charging/discharging control to the one-side dischargingcontrol, it is less likely that a blank period in which the power isinterrupted will occur in a period from the detection of the abnormalityin the conductive path 14 on the input side until the backup operationis performed.

According to the present configuration, the control unit 60 correspondsto an example of the abnormality detection unit and has at least afunction for detecting an abnormality (specifically, an abnormality inwhich the voltage of the conductive path 14 on the input side falls tothe first threshold voltage or lower) of the voltage of the conductivepath 14 on the input side. When the control unit 60 then detects thatthere is an abnormality while the charging/discharging control is beingperformed due to the mode setting in step S3, the mode is switched tothe first backup mode in step S6 and the one-side discharging control isperformed in which the operation of the first voltage conversion unit 40is stopped and the second voltage conversion unit 50 is caused toperform the discharging operation.

After the first backup mode (one-side discharging mode) has been set instep S6, the control unit 60 determines in step S7 whether a quickdischarging trigger has been reached (specifically, whether the outputvoltage of the second power supply unit 5 has dropped to a level equalto or below a second threshold voltage). According to thisconfiguration, the voltage of the conductive path 24 on the second powersupply unit side is input to the control unit 60 and the control unit 60monitors the voltage of the conductive path 24 on the second powersupply unit side. The control unit 60 determines in step S7 whether thevoltage of the conductive path 24 on the second power supply unit sidehas dropped to a level equal to or below the second threshold voltage,and if it is determined that the voltage of the conductive path 24 onthe second power supply unit side is equal to or less than the secondthreshold voltage (it is determined that the quick discharging triggerhas occurred, Yes in step S7), the control unit 60 performs theprocessing in step S8. However, if the control unit 60 determines thatthe voltage of the conductive path 24 on the second power supply unitside is not equal to or less than the second threshold voltage (No instep S7), the control unit 60 maintains the setting in step S6 (thefirst backup mode setting) and continues the abovementioned one-sidedischarging control.

When the control unit 60 determines in step S7 that the voltage of theconductive path 24 on the second power supply unit side is equal to orless than the second threshold voltage, the control unit 60 establishesa second backup mode (quick discharging mode) in step S8. The secondbackup mode (quick discharging mode) is a mode for the control unit 60to perform the quick discharging control. When performing the quickdischarging control, the control unit 60 turns off the semiconductorswitch 71 and keeps both of the semiconductor switches 72 and 73 on. Asa result, the flow of the current from the first conductive path 21 andthe second conductive path 22 toward the conductive path 14 on the inputside is interrupted, and a conductive state is established between thefirst conductive path 21 and the conductive path 16 on the output side.According to the above switch conditions, the first voltage conversionunit 40 and the second voltage conversion unit 50 are caused to performthe discharging operation (step-up operation) in which a dischargingcurrent flows as illustrated in FIG. 6. Specifically, the first voltageconversion unit 40 is caused to perform a step-up operation so as tostep-up the voltage of the conductive path 24 on the second power supplyunit side and output the voltage to the first conductive path 21, andthe second voltage conversion unit 50 is caused to perform a step-upoperation so as to step-up the voltage of the conductive path 24 of thesecond power supply unit side and output the voltage to the thirdconductive path 23.

According to the present configuration, the control unit 60 correspondsto an example of a voltage detection unit and functions so as to detectthe output voltage of the second power supply unit 5. The control unit60 functions so as to perform at least the quick discharging controlwhen the output voltage of the second power supply unit 5 detected bythe voltage detection unit is equal to or less than a fixed value.

Although omitted in FIG. 2, it is continuously determined that thevoltage of the conductive path 14 on the input side is equal to or lessthan the first threshold voltage during the quick charging mode (thatis, while the quick charging control is being performed) under thecontrols in FIG. 2, and when it is determined that the voltage of theconductive path 14 on the input side is equal to or less than the firstthreshold voltage, the processing from step S6 onward may be performed.Although omitted in FIG. 2, when it is determined that the charging iscompleted in step S5 and the operations of the first voltage conversionunit 40 and the second voltage conversion unit 50 are stopped, it iscontinuously determined that the voltage of the conductive path 14 onthe input side is equal to or less than the first threshold voltageuntil the ignition switch is turned off. When it is determined that thevoltage of the conductive path 14 on the input side is equal to or lessthan the first threshold voltage, the processing from step S6 onward maybe performed.

The following exemplifies effects of the present configuration.

The vehicle power supply device 1 is able to cause both the firstvoltage conversion unit 40 and the second voltage conversion unit 50 toperform charging operations as illustrated in FIG. 3 when the controlunit 60 performs the quick charging control. Because the charging timeof the second power supply unit 5 can be shortened due to the quickcharging control, the charging voltage of the second power supply unit 5can be easily raised in a short time to a suitable level, and thesituation in which the timing of the power supply being cut off arrivesduring the quick charging control is less likely to occur.

In addition, the first voltage conversion unit 40 is caused to perform acharging operation and the second voltage conversion unit 50 is causedto perform a discharging operation as illustrated in FIG. 4 when thecontrol unit 60 performs the charging/discharging control. That is,during the charging/discharging control in FIG. 4, even when,hypothetically, the power supply from the first power supply unit 3 isinterrupted during the charging due to the charging/discharging control,the charging state of the second power supply unit 5 is continuouslymaintained before and after the interruption because the dischargingoperation of the second power supply unit 5 can be continued by thesecond voltage conversion unit 50 while the charging operation of thesecond power supply unit 5 is being performed by the first voltageconversion unit 40.

Furthermore, because two useful controls can be used separately withregard to the “problem of the power supply of the first power supplyunit 3 being interrupted during charging” in this way, the above problemcan be addressed and freedom for charging the second power supply unit 5can be improved.

As illustrated in FIG. 2, the control unit 60 functions so as to performthe quick charging control when the ignition switch (starting switch)for switching to a state in which the vehicle in which the power supplydevice 1 is mounted can travel, is turned on, and so as to perform thecharging/discharging control after the ignition switch has been turnedon and the predetermined condition has been established. The powersupply device 1 configured in this way is able to promptly increase theoutput voltage because the charging is performed quickly after theignition switch has been turned on even when the output voltage of thesecond power supply unit 5 is at a relatively low level at the point intime that the ignition switch is turned on. That is, after the ignitionswitch has been turned on, the second power supply unit 5 can be made torecover in a short time from the low level state. When the predeterminedcondition has been established after starting the quick chargingcontrol, the quick charging control can be completed early and switchedto the charging/discharging control that is resistant to theinterruption of power of the first power supply unit 3 (a control inwhich, even if the power is interrupted, the discharging is maintainedat that point in time).

In addition, the control unit 60 performs the charging/dischargingcontrol when at least a shift operation has been performed in thevehicle in which the power supply device 1 is mounted after the ignitionswitch (starting switch) has been turned on. The vehicle power supplydevice 1 configured in this way is able to promptly increase the outputvoltage of the second power supply unit 5 before the vehicle travels andthe second power supply unit 5 can be recovered at an earlier stage froma low level state because the quick charging control can be performedbefore the shift operation is performed. The control can be switched tothe charging/discharging control after at least the shift operation hasbeen performed. That is, after the possibility of the vehicle entering atraveling state has been established, the complete cutoff of powerduring traveling can be prevented by switching to a control that isresistant to the power interruption of the first power supply unit 3 (acontrol in which, even when a power interruption occurs, discharging ismaintained at that point in time).

In addition, the control unit 60 performs the charging/dischargingcontrol when at least a fixed time period has elapsed after the ignitionswitch (starting switch) has been turned on. During the initial stageafter the ignition switch has been turned on and before the fixed timeperiod has elapsed, the vehicle power supply device 1 configured in thisway is able to promptly increase the output voltage of the second powersupply unit 5 and enable the second power supply unit 5 to recoverearlier from a low level state because the quick charging control can beperformed. After at least the fixed time period has elapsed, thecharging/discharging control can be completed at an earlier stage andthe control can be switched to the charging/discharging control that isresistant to the power interruption of the first power supply unit 3 (acontrol in which, even if the power is interrupted, the discharging ismaintained at that point in time).

The vehicle power supply device 1 has the semiconductor switch 73(switching unit) provided with: the switch part 73B that is disposed inthe third conductive path 23, has one end electrically connected to thesecond voltage conversion unit 50, has the other end electricallyconnected to the conductive path 16 on the output side, and switchesbetween on and off; and a diode 73A that is provided in parallel to theswitch part 73B, has an anode electrically connected to the secondvoltage conversion unit 50, and a cathode electrically connected to theconductive path 16 on the output side. The control unit 60 performs thequick charging control while the switch part 73B is on, and performs thecharging/discharging control while the switch part 73B is off. The powersupply device 1 configured in this way is able to allow the current toflow to the second voltage conversion unit 50 from the conductive path14 on the input side and through the second conductive path 22 and thethird conductive path 23, by turning on the switch part 73B of thesemiconductor switch 73 (switching unit) while performing the quickcharging control. Alternatively, while performing thecharging/discharging control, the power supply device 1 interrupts theflow of the current to the second voltage conversion unit 50 from theconductive path 14 on the input side and through the second conductivepath 22 and the third conductive path 23 by turning off the switch part73B, and enables the current output from the second voltage conversionunit 50 to flow toward the conductive path 16 on the output side due tothe presence of the diode 73A provided in parallel to the switch part73B.

The vehicle power supply device 1 is provided with the abnormalitydetection unit that detects at least an abnormality of the voltage ofthe conductive path 14 on the input side. The control unit 60 performsthe one-side discharging control in which the operation of the firstvoltage conversion unit 40 is stopped and the second voltage conversionunit 50 is caused to perform a discharging operation when an abnormalityis detected by the abnormality detection unit when the quick chargingcontrol or the charging/discharging control is being performed.

The power supply device 1 configured in this way is able to cause thesecond voltage conversion unit 50 to perform the discharging operationand maintain the power supply state while stopping the operation of thefirst voltage conversion unit 40 and carrying out protection because thecontrol unit 60 performs the one-side discharging control when anabnormality is detected by the abnormality detection unit while thequick charging control or the charging/discharging control are beingperformed. In particular, when the control is switched to the one-sidedischarging control when an abnormality occurs on the conductive path 14on the input side while the charging/discharging control is beingperformed, a situation is less likely to occur in which the power supplyimmediately after the occurrence of the abnormality is completelycutoff, because the discharging operation of the second voltageconversion unit 50 can be continued before and after the abnormality.

The power supply device 1 has the semiconductor switches 71 and 72(second switching unit) that switch between on, in which a currentbetween the conductive path 14 on the input side and the thirdconductive path 23 is allowed to flow, and off, in which said current isinterrupted. The control unit 60 turns on the semiconductor switches 71and 72 (second switching unit) while executing the quick chargingcontrol and the charging/discharging control, and turns off thesemiconductor switches 71 and 72 (second switching unit) while executingthe one-side discharging control.

When performing the quick charging control, the power supply device 1turns the semiconductor switches 71 and 72 (second switching unit) on(state that allows the current to flow between the conductive path 14 onthe input side and the third conductive path 23) and makes it possiblefor the current to flow from the conductive path 14 on the input sidethrough the second conductive path 22 and the third conductive path 23to the second voltage conversion unit 50. However, when the one-sidedischarging control is performed in response to the occurrence of anabnormality, the flow of the discharging current from the second voltageconversion unit 50 to the conductive path 14 on the input side where theabnormality occurred can be prevented because the semiconductor switches71 and 72 (second switching unit) are turned off.

The first voltage conversion unit 40 is able to perform the chargingoperation for stepping down the voltage applied to the first conductivepath 21 and outputting the voltage to the conductive path 24 on thesecond power supply unit side, and the discharging operation forstepping up the voltage applied to the conductive path 24 on the secondpower supply unit side and outputting the voltage to the firstconductive path 21. The control unit 60 is able to perform the quickdischarging control for causing the first voltage conversion unit 40 toperform the discharging operation and causing the second voltageconversion unit 50 to perform the discharging operation. The vehiclepower supply device 1 is able to cause either of the first voltageconversion unit 40 and the second voltage conversion unit 50 to performthe discharging operation as needed which is advantageous when it isdesirable to increase the discharging capacity of the second powersupply unit 5.

The power supply device 1 has the voltage detection unit for detectingthe output voltage of the second power supply unit 5. The control unit60 functions so as to perform at least the quick discharging controlwhen the output voltage of the second power supply unit 5 detected bythe voltage detection unit is equal to or less than a fixed value(second threshold voltage). According to the present configuration, thesecond power supply unit 5 can be used in a lower voltage range if thequick discharging control is performed when the output voltage of thesecond power supply unit 5 is low. Consequently, the voltage range inwhich use of the second power supply unit 5 is possible can be widened.

Other Embodiments

The present disclosure is not limited to the embodiment explained withreference to the above language and diagrams and the followingembodiments, for example, are included within the technical scope of thepresent disclosure.

In the first embodiment, the first voltage conversion unit 40 isconfigured to be able to perform the step-down operation for steppingdown the voltage applied to the first conductive path 21 and applyingthe voltage to the conductive path 24 on the second power supply unitside, and perform the step-up operation for stepping up the voltageapplied to the conductive path 24 on the second power supply unit sideand applying the voltage to the first conductive path 21. However, inthe first embodiment or any example in which the first embodiment ismodified, in a configuration in which the output voltage of the secondpower supply unit 5 is greater than the output voltage of the firstpower supply unit 3, the first voltage conversion unit 40 may beconfigured to perform the step-up operation (charging operation) forstepping up the voltage applied to the first conductive path 21 andapplying the voltage to the conductive path 24 on the second powersupply unit side, and the step-down operation (discharging operation)for stepping down the voltage applied to the conductive path 24 on thesecond power supply unit side and applying the voltage to the firstconductive path 21. Similarly, the second voltage conversion unit 50 maybe configured to perform the step-up operation (charging operation) forstepping up the voltage applied to the third conductive path 23 andapplying the voltage to the conductive path 24 on the second powersupply unit side, and the step-down operation (discharging operation)for stepping down the voltage applied to the conductive path 24 on thesecond power supply unit side and applying the voltage to the thirdconductive path 23.

While an example is described in the first embodiment in which the firstvoltage conversion unit 40 and the second voltage conversion unit 50 areboth configured as single phase DCDC converters, one or both of thefirst voltage conversion unit 40 and the second voltage conversion unit50 may be configured as multi-phase DCDC converters in the firstembodiment or any example in which the first embodiment is modified. Forexample, when a multiphase structure is established in which a pluralityof the first voltage conversion units 40 illustrated in FIG. 1 areprovided, the drain of the switching element 41 and one end of thecapacitor 44 in each of the first voltage conversion units 40 may beelectrically connected to the first conductive path 21, one end of theinductor 43 of each of the first voltage conversion units 40 may beconnected to the conductive path 24 on the second power supply unitside, and the other end of the capacitor 44 and the source of theswitching element 42 of each of the first voltage conversion units 40may be connected in parallel so as to be electrically connected to oneend (end part on opposite side from the ground) of the resistor 83A.Additionally, when a multiphase structure is established in which aplurality of the second voltage conversion units 50 illustrated in FIG.1 are provided, the drain of the switching element 51 and one end of thecapacitor 54 of each of the second voltage conversion units 50 may beelectrically connected to the third conductive path 23, one end of theinductor 43 of each of the second voltage conversion units 50 may beelectrically connected to the conductive path 24 on the second powersupply unit side, and the other end of the capacitor 54 and the sourceof the switching element 52 of each of the second voltage conversionunits 50 may be connected in parallel so as to be electrically connectedto one end of the resistor 83A.

While the first embodiment describes an example in which both the firstvoltage conversion unit 40 and the second voltage conversion unit 50 areconfigured as synchronous rectification DCDC converters, the firstvoltage conversion unit 40 and the second voltage conversion unit 50 maybe configured as diode-type DCDC converters in which a portion of theswitching elements are replaced by diodes in the first embodiment or anyexample in which the first embodiment is modified.

While the first embodiment describes a configuration for detecting thatthe ignition switch (starting switch) is on by means of the ignitionon-signal, a configuration may be used in which the fact that theignition switch has been turned on is identified in the first embodimentor any example in which the first embodiment is modified. For example, acase in which communication is possible with an in-vehicle communicationsystem such as CAN and the like may be used as a case in which thestarting switch is on.

In addition, the starting switch is not limited to an ignition switchand an electric vehicle system (EV system) or the like may be used when,for example, the vehicle is an electric vehicle or the like.

While switching elements configured as N-channel MOSFETs are describedas the semiconductor switches 71, 72, and 73 and the switching elements41, 42, 51, and 52, the switching elements may be P-channel MOSFETs, maybe other switching elements such as bipolar transistors or IGBTs and thelike, or a portion thereof may be replaced by mechanical relays in thefirst embodiment or any example in which the first embodiment ismodified.

While the control unit 60 corresponding to the abnormality detectionunit determines that there is an abnormality when a voltage drop isdetected in the conductive path 14 on the input side in step S4 in FIG.2 in the first embodiment, an abnormality may be determined when anovervoltage state is detected in which the voltage of the conductivepath 14 on the input side exceeds a predetermined overvoltage threshold,or an abnormality may be determined when an overcurrent state isdetected in which the current of the conductive path 14 on the inputside exceeds a predetermined overcurrent threshold in the firstembodiment or any example in which the first embodiment is modified. Forexample, the control unit 60 may advance the processing to step S6 whenthe aforementioned overcurrent state abnormality is detected by theabnormality detection unit while the quick charging control or thecharging/discharging control is being performed, and the control unit 60may perform the one-side discharging control so as to stop the operationof the first voltage conversion unit 40 and cause the second voltageconversion unit 50 to perform the discharging operation.

1. A vehicle power supply device comprising: a first conductive path electrically connected to a conductive path on an input side that serves as a power pathway from a first power supply; a second conductive path that is electrically connected to the conductive path on the input side and branches off as a path different from the first conductive path, and is electrically connected to a conductive path on an output side; a third conductive path that is electrically connected to the second conductive path and the conductive path on the output side; a first voltage converter that performs at least a charging operation for stepping up or stepping down the voltage applied to the first conductive path and applying an output voltage to a conductive path on a second power supply side connected to the second power supply; a second voltage converter that performs at least a charging operation for stepping up or stepping down a voltage applied to the third conductive path and applying an output voltage to the conductive path on the second power supply side, and a discharging operation for stepping up or stepping down a voltage applied to the conductive path on the second power supply side and applying an output voltage to the third conductive path; and a control unit that performs at least a quick charging control which causes the first voltage converter to perform the charging operation and causes the second voltage converter to perform the charging operation, and a charging/discharging control which causes the first voltage converter to perform the charging operation and causes the second voltage converter to perform the discharging operation.
 2. The vehicle power supply device according to claim 1, wherein the control unit performs the quick charging control when a starting switch for switching a vehicle in which the power supply device is mounted to a state which allows travel, is turned on, and performs the charging/discharging control when a predetermined condition is established.
 3. The vehicle power supply device according to claim 2, wherein the control unit performs the charging/discharging control when at least a shift operation of the vehicle in which the power source device is mounted is performed after the starting switch has been turned on.
 4. The vehicle power supply device according to claim 2, wherein the control unit performs the charging/discharging control when at least a fixed time period has elapsed after the starting switch has been turned on.
 5. The vehicle power supply device according to claim 1, further comprising: a switch provided with: a switch part, which is disposed in the third conductive path, one end side of which is electrically connected to the second voltage converter, the other end side of which is electrically connected to the conductive path on the output side, and which switches between on and off; and a diode provided parallel to the switch, having an anode electrically connected to the second voltage converter, and a cathode electrically connected to the conductive path on the output side, wherein the control unit performs the quick charging control while the switch part is on and performs the charging/discharging control while the switch part is off.
 6. The vehicle power supply device according to claim 1, further comprising: an abnormality detector that detects at least an abnormality of the voltage or current of the conductive path on the input side, wherein, when an abnormality is detected by the abnormality detector while the quick charging control or the charging/discharging control is being performed, the control unit performs at least a one-side discharging control for stopping operation of the first voltage converter and for causing the second voltage converter to perform the discharging operation.
 7. The vehicle power supply device according to claim 6 further comprising: a second switch for switching between on, in which the flow of current between the conductive path on the input side and the third conductive path is allowed, and off, in which said flow is interrupted, wherein the control unit turns the second switch on when executing the quick charging control and the charging/discharging control, and turns the second switch off when executing the one-side discharging control.
 8. The vehicle power supply device according to claim 1, wherein the first voltage converter performs a charging operation for stepping up or stepping down a voltage applied to the first conductive path and outputting the voltage to the conductive path on the second power supply side, and a discharging operation for stepping up or stepping down a voltage applied to the conductive path on the second power supply side and outputting the voltage to the first conductive path; and the control unit at least performs a quick discharging control for causing the second voltage converter to perform a discharging operation while causing the first voltage converter to perform a discharging operation.
 9. The vehicle power supply device according to claim 8, further comprising: a voltage detector for detecting the output voltage of the second power supply, wherein the control unit performs the quick discharging control when at least the output voltage of the second power supply detected by the voltage detector is equal to or less than a fixed value. 